CD-ROM and DVD-ROM read-only disc-shaped media, and CDR, CD-RW, DVD-R, DVD-RW, and DVD-RAM recordable disc-shaped media, as storage media for personal computers, and devices for recording, recording and reproducing, or recording, erasing, and reproducing these disc-shaped media have become widespread.
There has been a shift in interest from read-only disc-shaped media, which are designed to handle only pre-recorded data, to recordable disc-shaped media that allow users to input and save data. In particular, in order to store image data, in recent years much energy has been poured into developing recordable discs capable of holding large volumes of data. For example, DVD-R, DVD-RW, and DVD-RAM discs (these three are hereinafter referred to as “recordable discs”), which have much larger storage capacities than CD-R or CD-RW discs, have been developed and becoming more popular.
On the other hand, it is desirable that recording speeds are increased in order to record large volumes of information signals to large capacity recordable discs. High-speed recording technologies have begun to be developed for devices for recording and reproducing, or recording, erasing, and reproducing, recordable discs (hereinafter, these are referred to as recording devices).
Recording devices must be compatible with a plurality of types of recordable discs with different recording capacities. Recording devices also must be able to handle a plurality of different recording speeds. With a recording device for DVD-RAM discs, for example, at present recording can be carried out at two recording speeds, normal speed and double speed. Thus, in conventional DVD-RAM discs, as shown in FIG. 15, identifiers indicating that recording at double speed is possible are recorded as non-rewritable pits to a pit portion provided in the lead-in region of the disc substrate. Also, conventional DVD-RAM recording devices were configured so that when a new DVD-RAM disc was placed in the device, the device would read information written in the pit portion to ascertain the recording speed of that disc and carry out recording at the recording speed that was ascertained.
However, high-speed recording continues to be a high priority for recording devices, and conventionally there has been a clear demand for recording speeds of at least triple speed (hereinafter, referred to as “high speed” in this specification). For example, with recordable discs compatible with low speeds such as double speed, for example, as mentioned above, the information on the compatible recording speeds was recorded as pits in the pit portion of the lead-in region of the disc, allowing the recording speed to be controlled. However, the following problems occurred when using recordable discs capable of not only the normal recording speed but also high recording speeds of triple and quadruple speed, for example, in addition to double speed.
That is, different recording speeds result in changes in specific and very important recording conditions of recordable discs, such as the intensity of the light beam that is irradiated onto the information layer when a user records desired data and the mode of pulse modulation. Consequently, in the case of a recordable disc that can be recorded at a plurality of different high speeds, when the above conventional technology is adapted without modification, information on the plurality of recording conditions corresponding to the recording speeds must be recorded as pits in the lead-in region in addition to the identifiers indicating which recording speeds can be handled.
However, with conventional recording devices performing recording control simply by detecting only the pit portion there was a risk that factors such as incorrect detection of the pit portion, for example, would result in insufficient reliability with respect to appropriate recording. Consequently, to ensure recording reliability, it is necessary to record identifiers and information on the recording conditions twice or three times in the lead-in region.
There are also the following problems with respect to the manufacture of recordable discs. That is, the pit portion of the lead-in region was formed in a non-rewritable format on the disc substrate using a stamper having a surface configuration that corresponds to pits. Thus, conventionally it was necessary to prepare a dedicated stamper for each disc capable of adapting to different recording speeds. Accordingly, the following problem is conceivable. To take an example, if discs capable of recording at high speeds of quadruple speed or more are mainstream, then a sudden increase in demand for recordable discs designed for triple speed or less would mean that the substrates for recordable discs that can be recorded at high recording speeds of quadruple speed or more could not be used as the substrates for recordable discs designed for triple speed or less. This is because the identifiers that are recorded in the pit portion of substrates for recording discs designed for quadruple speed or more as non-rewritable pits are different from the identifiers for recordable discs that are triple speed or less. Consequently, in such a case, it would be necessary to remanufacture a stamper for forming non-rewritable identifiers for triple speed or less in the pit portion and to manufacture disc substrates using this stamper. Therefore, the inability to quickly respond to changes in the demand for discs is a foreseeable problem.
In the case of phase-change recordable discs such as DVD-RAM discs, at a minimum the data region is phase-changed to an erased state (ordinarily this is done through crystallization, and thus will be referred to as initializing crystallization, crystallization, initialization, or initializing, for example) so that in general users can record desired information. Then, information indicating which recording operation to use with respect to the disc and information on the recording devices capable of recording to the disc, for example, are recorded in the recordable portion of the lead-in region and the disc is shipped.
With phase-change recordable discs as well, conventionally the identifiers specifying compatible recording speeds were recorded in the pit portion of the lead-in region. However, there are instances in which even though identifiers indicating that the disc can be recorded at quadruple speed or more, for example, are formed in the pit potion of the lead-in region of the substrate, some problem in the process for forming the information layer on the substrate results in the disc being found to be incompatible with quadruple speed prior to shipping. In such instances, even though the disc can be recorded at triple speed or less without problems, the recordable disc that has been produced is discarded, and this wastes resources and/or energy.